1. Field of the Invention
This invention pertains generally to video processing, and more particularly to the compression and decompression of video within video memory prior to encoding or output.
2. Description of Related Art
A typical video architecture is implemented to preprocess video data prior to storing it in a video frame memory typically accessed through an external bus. The video data is then retrieved from the video memory during an encoding process and/or for output. The amount of data transfer between the encoder and the video memory over the bus may be very large, leading to the need for large amounts of video memory, requiring enormous memory bus bandwidth, and consequently leading to high power consumption.
FIG. 1 shows a conventional video camera or still-picture camera architecture. The input video obtained by an input device, such as CCD or CMOS sensors, is then stored in an external memory after being preprocessed. In general preprocessing comprises noise reduction and video data conversion from RGB (Red, Green, Blue) to YUV (one luminance Y, two chrominance U+V). Other processing devices, such as a video encoder or a display device, then read the video data from the video memory.
Since the amount of video data is generally large, the required bus bandwidth for video data transfer through the external bus is significantly high. In particular with regard to HD (High Definition) video application, the required bus bandwidth is enormous, wherein bandwidth cost as well as power consumption become very high making it difficult to implement low-cost image/video systems.
Another technical challenge in video camera systems is in regard to the required memory size. Most video devices are implemented in Soc (System on Chip). In general, the cost of an external memory (such as SDRAM) is generally higher than other devices. Therefore, a reduction of required memory size allows the overall system cost to be reduced.
Accordingly, a need exists for a method for reducing necessary storage bandwidth and memory for video data streams, and in particular when performed prior to the video encoding process. The present invention fulfills that need as well as others and overcomes the limitations of prior solutions.